The present invention relates to a method for the fabrication of patterned poled dielectric structures and devices. Such devices are useful for generating optical frequency conversion, by creating quasi-phase matching between two optical signals.
Patterned poled dielectric structures and devices offer the possibility of making optical frequency conversion. This has many applications in the field of optics. For example, such devices can be used to create second harmonic generation (SHG) of a laser signal in order to obtain a shorter wavelength signal. Other applications include sum frequency generation (SFG) and difference frequency generation (DFG). In fact, in association with a parametric oscillator, these devices can be used to make frequency tunable laser source, offering a very wide band of wavelength output. Frequency conversion is also sought after for network reconfiguration in wavelength division multiplexing systems.
The two most commonly known methods of fabrication of domain inversion patterns in ferroelectric materials are very similar to one another, and are described in U.S. Pat. Nos. 5,193,023 and 5,519,802. Both of these patents describe the use of a patterned electrode structure to make a domain inversion in ferroelectric materials; however, different techniques are proposed. Although these techniques have proven successful, making the needed electrode pattern is a complex and time-consuming process that is not perfectly reliable.
In U.S. Pat. No. 5,875,053, there is described an allegedly more production-friendly technique for the fabrication of these elements, which is based on using very simple, single, planar-applied liquid electrodes. In order to create the domain inversion pattern, electric insulators are locally implanted underneath one of the electrodes. The local electrical insulation is insured by impurity diffusion or local treatment of the ferroelectric material by an electron beam. Although the electrode structure is much simpler, the method for implanting local insulator regions in the ferroelectric material is not, and is associated with very complex, high-cost and not commonly available material.
It is thus an object of the invention to provide a simple, reproducible and economical method for the fabrication of patterned, poled dielectric structures or devices.
In accordance with the invention, this object is achieved with a method for fabricating a patterned, poled dielectric structure, comprising the steps of providing a material having a first and second surfaces, patterning a period pattern into the first surface, applying an electrode to the first surface, applying another electrode to the second surface, and applying a voltage between the electrodes to create a domain inversion in the material.
Preferably, the material is a ferroelectric material, and the electrode is a single, planar, solid electrode.